Economists said the £11.4 billion surplus was neither enough to save Chancellor George Osborne from busting his deficit target by up to £10 billion this year, nor to ease expectations that Britain’s rating will soon be downgraded.

The January figure was healthier than the City expected and easily exceeded the £6.4 billion surplus a year ago. It followed the traditional surge in tax revenues at this time, plus £3.8 billion that was down to including interest from the Bank of England’s quantitative easing programme for the first time.

Total receipts including taxes rose by seven per cent or £4.5 billion to £65.8 billion.

However, the picture covering the first nine months of the tax year was gloomy, with public borrowing £1.5 billion higher than a year earlier at £93.8 billion.

Economist Howard Archer, of financial analysts and forecasters IHS GlobalInsight, said Mr Osborne was likely to borrow £3 billion more than his target.

“While better than expected, the January public finance data will likely do little to dilute high expectations that at least one of the credit rating agencies will strip the UK of its AAA rating in the near term,” he said.

Labour spokesman Chris Leslie called for a change of plan. He said: “Strip away the smoke and mirrors, like the transfer of cash from the Bank of England, and underlying borrowing so far this year is rising and is £5.3 billion higher than the same period last year.

“A flatlining economy means that the Government is borrowing more to pay for economic failure as the welfare bill is up.”

With every penny counting, Mr Osborne was dismayed that the auction of 4G mobile airwaves raised £1.2 billion less than hoped.

Chris Williamson, chief economist at independent financial information services company Markit, estimated Mr Osborne is likely to miss his borrowing target by between £5 billion and £10 billion and warned that the UK’s AAA credit rating is “looking increasingly at risk”.

He added: “Without a credible plan from the Government to break the vicious circle of a sluggish economy, low tax revenues and rising public sector borrowing, the credit rating agencies are likely to lose their patience.”

A Treasury spokesman insisted today’s public finance figures showed an improving picture, adding they “underline what the Governor of the Bank of England said last week: the road ahead will be difficult, but the economy is on the right track.”